#include <iostream>
#include <Eigen/Dense>  // Eigen header file

int main(int argc, char **argv) {
    std::cout << "Hello, world!" << std::endl;
    std::cout << "hello, eigen!" << std::endl;

    // MatrixXd is dynamic array ,init matrix row and col
    Eigen::MatrixXd m(2,2);
    // matrix assignment
    m(0,0) = 3;
    m(1,0) = 2.5;
    m(0,1) = -1;
    m(1,1) = m(1,0) + m(0,1);

    // matrix output
    std::cout << m << std::endl;
    return 0;
}
